The Cool Jazz goes along the shore and you stop to swim for about 30 minutes.( see pic )
The water is often rougher than if you've ever gone in Negril - but we enjoy it much more - and the Crew is a little more upbeat - dancing and entertaining. Also, you board from the Pier so you don't have to walk out into the water carrying your bags and towels.
My advice, is not to wear your wedding rings, as a Newleywed lost his when we were there 2 weeks ago - it was not found.

As I remember, the CTI cat cruise leaves about 4:00 and takes about 2-1/2 to 3 hours. They serve rum punch and beer and play Jamaican music. It does have a bathroom. It travels along the shoreline, and halfway through it stops in a calm bay where people can jump off the cat slide and swim for awhile. You should wear a swimsuit and bring a camera and towel. It is recommended that you bring waterproof baggies as water can crash onto the deck. It can get cool during the return trip so you may want to bring a coverup in addition to your towel. They also sell CD's, jewelry and shells on the boat, so you might want to also bring some money for that. Also, the people operating the cruise are not part of Couples so you might want to bring tip money (typically $5-$10). One other item, if you have any tendency to motion sickness, it is suggested that you should take dramamime, ginger pills, or some other motion sickness remedy.

we have been on the cat cruise many times and find that the ones that get sick are the ones that drink to much before they get on the boat or the ones that have to much of the punch while on the boat but fear not the ropes on the sides are very sturdy and will hold up nicely while you get a closre look at the water!!!